The utility of plastics in modern manufacturing stems from their diverse mechanical properties, allowing them to replace traditional materials like glass and metal. Defining a “strong” plastic requires considering how a material resists various types of mechanical stress, rather than relying on a single measurement. The selection of a polymer depends on the combination of performance attributes it exhibits under load for a specific application.
What Makes a Plastic Strong
Defining a plastic’s strength involves several distinct measurements of how it reacts to external forces. Stiffness, measured as the elastic modulus, describes a material’s resistance to elastic deformation when a load is applied. A stiff plastic maintains its shape and requires a large force to cause a small change in form. This property contrasts with toughness, which is the material’s ability to absorb energy before fracturing, often measured as impact resistance.
A tough plastic may deform significantly under stress but avoids catastrophic failure. Conversely, a stiff material might break suddenly in a brittle fashion if the stress exceeds its limit. Tensile strength is another important metric, measuring the maximum pulling force a material can withstand before it breaks or permanently deforms. This measurement is relevant for parts that are constantly being stretched or pulled apart.
Flexural strength measures a plastic’s ability to resist failure when subjected to bending forces, which is a combination of tension and compression. High flexural strength is necessary for components like plastic beams or shelving that must support a load without excessive deflection. A truly “strong” plastic possesses an optimal balance of high tensile strength, high flexural strength, and significant impact toughness for its intended application.
Common Examples of High Strength Plastics
Polycarbonate (PC) is recognized for its exceptional impact resistance, making it virtually shatterproof. This transparency and extreme toughness lead to its use in demanding applications like safety glasses, machine guards, and the transparent layers of “bulletproof” glass. PC also offers high dimensional stability and retains strength across a wide range of temperatures, ensuring reliability in electronic device housings and automotive components.
Acrylonitrile Butadiene Styrene (ABS) achieves balanced strength through its three-component structure. The butadiene component, a rubbery phase, provides excellent toughness and shock absorption, preventing brittle failure. The acrylonitrile and styrene components contribute thermal stability, chemical resistance, and rigidity. This combination makes ABS a preferred material for durable consumer products like Lego bricks, automotive interior trim, and protective equipment casings.
Nylon (Polyamide or PA) is widely used as an engineering plastic due to its high abrasion resistance and exceptional durability. Strong hydrogen bonds in the polymer chains resist wear from repeated rubbing or sliding contact. This characteristic, paired with a naturally low coefficient of friction, allows Nylon to be self-lubricating. Consequently, Nylon is the standard choice for mechanical parts involving movement and friction, such as gears, bearings, and bushings.
Specialized and Reinforced Super Polymers
Specialized super polymers offer greater performance for environments that exceed the limits of common engineering plastics. Polyether Ether Ketone (PEEK) is a high-performance thermoplastic known for its thermal and chemical stability. PEEK maintains high tensile and flexural strength at continuous service temperatures up to 260°C, making it suitable for aerospace and automotive engine components. Its biocompatibility and resistance to sterilization cycles also make it a preferred material for spinal implants and surgical devices.
Ultra-High Molecular Weight Polyethylene (UHMWPE) is known not for high-temperature resistance but for its extraordinary wear and abrasion resistance. This is due to its extremely long polymer chains, with molecular weights several times higher than standard polyethylene. UHMWPE is used in high-wear industrial applications like chute liners and conveyor components. Its low friction and biocompatibility have also made it the standard for the bearing surface in total hip and knee joint replacements.
Standard plastics are often enhanced by incorporating fibers to create a composite material, dramatically increasing strength. Adding glass or carbon fibers stiffens the polymer matrix, which significantly increases the material’s tensile and flexural strength. Carbon Fiber Reinforced Plastic (CFRP) achieves an extremely high strength-to-weight ratio, making it five times lighter than steel while offering comparable strength. These reinforced composites are essential in structural applications across the automotive, sports equipment, and aerospace industries.